21802978 has 16 divisors (see below), whose sum is σ = 34040160. Its totient is φ = 10465056.

The previous prime is 21802961. The next prime is 21802987. The reversal of 21802978 is 87920812.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2926 + ... + 7222.

It is an arithmetic number, because the mean of its divisors is an integer number (2127510).

Almost surely, 2^21802978 is an apocalyptic number.

21802978 is a deficient number, since it is larger than the sum of its proper divisors (12237182).

21802978 is a wasteful number, since it uses less digits than its factorization.

21802978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4401.

The product of its (nonzero) digits is 16128, while the sum is 37.

The square root of 21802978 is about 4669.3659098426. The cubic root of 21802978 is about 279.3649638970.

The spelling of 21802978 in words is "twenty-one million, eight hundred two thousand, nine hundred seventy-eight".